StringCchCopyExA function

Copies one string to another. The size of the destination buffer is provided to the function to ensure that it does not write past the end of the buffer.

StringCchCopyEx adds to the functionality of StringCchCopy by returning a pointer to the end of the destination string as well as the number of characters left unused in that string. Flags may also be passed to this function for additional control.

StringCchCopyEx is a replacement for the following functions:

Syntax

STRSAFEAPI StringCchCopyExA(
  STRSAFE_LPSTR  pszDest,
  size_t         cchDest,
  STRSAFE_LPCSTR pszSrc,
  STRSAFE_LPSTR  *ppszDestEnd,
  size_t         *pcchRemaining,
  DWORD          dwFlags
);

Parameters

pszDest

Type: LPTSTR

The destination buffer, which receives the copied string.

cchDest

Type: size_t

The size of the destination buffer, in characters. This value must equal the length of pszSrc plus 1 to account for the copied source string and the terminating null character. The maximum number of characters allowed is STRSAFE_MAX_CCH.

pszSrc

Type: LPCTSTR

The source string. This string must be null-terminated.

ppszDestEnd

Type: LPTSTR*

The address of a pointer to the end of pszDest. If ppszDestEnd is non-NULL and any data is copied into the destination buffer, this points to the terminating null character at the end of the string.

pcchRemaining

Type: size_t*

The number of unused characters in pszDest, including the terminating null character. If pcchRemaining is NULL, the count is not kept or returned.

dwFlags

Type: DWORD

One or more of the following values.

Value Meaning
STRSAFE_FILL_BEHIND_NULL
0x00000200
If the function succeeds, the low byte of dwFlags (0) is used to fill the uninitialized portion of pszDest following the terminating null character.
STRSAFE_IGNORE_NULLS
0x00000100
Treat NULL string pointers like empty strings (TEXT("")). This flag is useful for emulating functions such as lstrcpy.
STRSAFE_FILL_ON_FAILURE
0x00000400
If the function fails, the low byte of dwFlags (0) is used to fill the entire pszDest buffer, and the buffer is null-terminated. In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string returned is overwritten.
STRSAFE_NULL_ON_FAILURE
0x00000800
If the function fails, pszDest is set to an empty string (TEXT("")). In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string is overwritten.
STRSAFE_NO_TRUNCATION
0x00001000
As in the case of STRSAFE_NULL_ON_FAILURE, if the function fails, pszDest is set to an empty string (TEXT("")). In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string is overwritten.

Return Value

Type: HRESULT

It is strongly recommended that you use the SUCCEEDED and FAILED macros to test the return value of this function.

Return code Description
S_OK
Source data was present, fully copied without truncation, and the resultant destination buffer is null-terminated.
STRSAFE_E_INVALID_PARAMETER
Either pszDest is NULL when there is source data present to copy, or an invalid flag was passed.
STRSAFE_E_INSUFFICIENT_BUFFER
The copy operation failed due to insufficient buffer space. Depending on the value of dwFlags, the destination buffer may contain a truncated, null-terminated version of the intended result. In situations where truncation is acceptable, this may not necessarily be seen as a failure condition.
 

Note that this function returns an HRESULT value, unlike the functions that it replaces.

Remarks

Compared to the functions it replaces, StringCchCopyEx provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCchCopyExalways null-terminates and never overflows a valid destination buffer, even if the contents of the source string change during the operation.

Behavior is undefined if the strings pointed to by pszSrc and pszDest overlap.

Neither pszSrc nor pszDest should be NULL unless the STRSAFE_IGNORE_NULLS flag is specified, in which case both may be NULL. However, an error due to insufficient space may still be returned even though NULL values are ignored.

StringCchCopyEx can be used in its generic form, or in its more specific forms. The data type of the string determines the form of this function that you should use.

String Data Type String Literal Function
char "string" StringCchCopyExA
TCHAR TEXT("string") StringCchCopyEx
WCHAR L"string" StringCchCopyExW

Requirements

   
Minimum supported client Windows XP with SP2 [desktop apps | UWP apps]
Minimum supported server Windows Server 2003 with SP1 [desktop apps | UWP apps]
Target Platform Windows
Header strsafe.h

See Also

Reference

StringCbCopyEx

StringCchCopy